A degree of immunity to influenza B is usually acquired

There are three types of influenza virus: Influenzavirus A, Influenzavirus B or Influenzavirus C. The cell-mediated immune response is important in viral clearance. Sometimes confused with the common cold, influenza is a much more severe disease and caused by a different type of virus. Types of influenza virus The influenza virus is an RNA virus of the family Orthomyxoviridae, which comprises the influenzaviruses, Isavirus and Thogotovirus. Influenza, commonly known as the flu, is an infectious disease of birds and mammals caused by an RNA virus of the family Orthomyxoviridae (the influenza viruses). The type A viruses are the most virulent human pathogens among the three influenza types and cause the most severe disease. As a result of this lack of antigenic diversity, a degree of immunity to influenza B is usually acquired at an early age. In more serious cases, influenza causes pneumonia, which can be fatal particularly in young children and the elderly